1. a combining form occurring in loanwords from Greek and Latin, where it meant “eight” ( octagon; octastyle ), on this model, used in the formation of compound words, and in chemical terms specialized to mean “having eight atoms” ( octavalent ).



/ ˈɒktə /


  1. a variant spelling of okta




  1. a variant of octo-
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Word History and Origins

Origin of octa-1

< Greek okta-, combining form of oktṓ eight
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Example Sentences

After this Eosa and the rest that fled, being encouraged by Octa's success, came also, and were admitted to the same favour.

The incautious sovereign having assented to this, Octa and Ebusa arrived with forty ships.


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Words That Use Octa-

What does octa- mean?

Octa- is a combining form used like a prefix meaning “eight.” It is often used in a great many scientific and technical terms.

Octa- comes from Greek oktṓ, meaning “eight.” The Latin equivalent, which is almost identical in spelling and pronunciation, is octō.

What are variants of octa-?

When combined with words or word elements that begin with a vowel, octa- becomes oct-, as in octane. Another variant of octa- is octo-, as in octofoil.

Want to know more? Check out our Words That Use entries for both oct– and octo-.

Examples of octa-

An example of a word you may have encountered that features octa- is octagon, “a polygon having eight angles and eight sides.” Octagon comes from Greek oktágōnos, which features the equivalent of the form octa-.

We know octa- means “eight,” but what about the -gon portion of the word? The form -gon, from Greek gōnía, means “angled, angular.” Octagon literally translates to “eight-angled.”

What are some words that use the combining form octa-?

What are some other forms that octa- may be commonly confused with?

Break it down!

The combining form -hedron means “face” and is used in the names of geometric figures with a certain number of faces. With this in mind, what is an octahedron?